Current studies of the (CNS) to astrocytes, many of which are potentially relevant to stroke. To better understand astrocyte function, we are studying transcriptional regulation of the human gene encoding glial fibrillary acidic protein (GFAP), the major component of astrocyte intermediate filaments. As the activity of this gene is regulated developmentally and in response to injury, these studies should lead to the identification of signaling pathways operating in these processes. In addition, by identifying the region of GFAP gene responsible for its specific expression in astrocytes, we can direct expression of other genes to these cells in transgenic animals. We are presently conducting site-directed mutagenesis within 120 bp sequence we previously identified as capable of endowing cell specificity to pinpoint the regions required for this function. Preliminary results indicate that mutation of either of several subregions enables expression in a non-astrocytic cell line, while having little effect on expression in an astrocytic cell line, suggesting that specificity is under negative control. In transgenic studies, the ability of the GFAP promoter we have isolated to direct expression of transgenes to astrocytes is now well established, so we have turned to modifying it to increase its utility. We are testing both tetracycline- and ecdysone-regulatable versions, as well as ones containing additional copies of enhancer elements. Finally, as a result of studies with mice genetically engineered to have a defective GFAP gene, we have discovered a vital role for GFAP in protecting against cervical spinal cord injury. This finding should contribute to a better understanding of the normal development, structure and physiology of the CNS that confers resistance to CNS trauma.